39,552 research outputs found
A Study of Different Modeling Choices For Simulating Platelets Within the Immersed Boundary Method
The Immersed Boundary (IB) method is a widely-used numerical methodology for
the simulation of fluid-structure interaction problems. The IB method utilizes
an Eulerian discretization for the fluid equations of motion while maintaining
a Lagrangian representation of structural objects. Operators are defined for
transmitting information (forces and velocities) between these two
representations. Most IB simulations represent their structures with
piecewise-linear approximations and utilize Hookean spring models to
approximate structural forces. Our specific motivation is the modeling of
platelets in hemodynamic flows. In this paper, we study two alternative
representations - radial basis functions (RBFs) and Fourier-based
(trigonometric polynomials and spherical harmonics) representations - for the
modeling of platelets in two and three dimensions within the IB framework, and
compare our results with the traditional piecewise-linear approximation
methodology. For different representative shapes, we examine the geometric
modeling errors (position and normal vectors), force computation errors, and
computational cost and provide an engineering trade-off strategy for when and
why one might select to employ these different representations.Comment: 33 pages, 17 figures, Accepted (in press) by APNU
Shape Animation with Combined Captured and Simulated Dynamics
We present a novel volumetric animation generation framework to create new
types of animations from raw 3D surface or point cloud sequence of captured
real performances. The framework considers as input time incoherent 3D
observations of a moving shape, and is thus particularly suitable for the
output of performance capture platforms. In our system, a suitable virtual
representation of the actor is built from real captures that allows seamless
combination and simulation with virtual external forces and objects, in which
the original captured actor can be reshaped, disassembled or reassembled from
user-specified virtual physics. Instead of using the dominant surface-based
geometric representation of the capture, which is less suitable for volumetric
effects, our pipeline exploits Centroidal Voronoi tessellation decompositions
as unified volumetric representation of the real captured actor, which we show
can be used seamlessly as a building block for all processing stages, from
capture and tracking to virtual physic simulation. The representation makes no
human specific assumption and can be used to capture and re-simulate the actor
with props or other moving scenery elements. We demonstrate the potential of
this pipeline for virtual reanimation of a real captured event with various
unprecedented volumetric visual effects, such as volumetric distortion,
erosion, morphing, gravity pull, or collisions
A Survey of Ocean Simulation and Rendering Techniques in Computer Graphics
This paper presents a survey of ocean simulation and rendering methods in
computer graphics. To model and animate the ocean's surface, these methods
mainly rely on two main approaches: on the one hand, those which approximate
ocean dynamics with parametric, spectral or hybrid models and use empirical
laws from oceanographic research. We will see that this type of methods
essentially allows the simulation of ocean scenes in the deep water domain,
without breaking waves. On the other hand, physically-based methods use
Navier-Stokes Equations (NSE) to represent breaking waves and more generally
ocean surface near the shore. We also describe ocean rendering methods in
computer graphics, with a special interest in the simulation of phenomena such
as foam and spray, and light's interaction with the ocean surface
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